Add Hotspot Toggle widget on WidgetLocker lockscreen. You can find many such toggle widgets in Play Store. Personally, I use Widgetsoid (it has lots of toggles). Hotspot Toggle is great if you are interested in only Hotspot toggle.

Technically, I am the winner because its a 1-step solution. All you need is to tap the Hotspot Toggle widget on lockscreen. You don't need to even unlock. :)